Question

[MATLAB] Write a function called myMultProd.m that computes the cumulative product of the elements in a vector. The cumulative product, pj, of the jth element of the vector x, xj, is defined by pj = (x1)(x2) … (xj) for j = 1:length of the vector x. DO NOT USE CUMPROD For example, when you run your function it should look like this:

>> x = [2 3 4 2]; >> myMultProd(x) >> ans = 2 6 24 48 That is, the function returns: 2, 2*3, 2*3*4, 2*3*4*2 where 2 is p1, 2*3 is p2, 2*3*4 is p3, etc.

a) Do this first using two for loops to explicitly carry out the calculation element-byelement. The inner loop should accumulate the product and the other loop should move through the elements of the vector p.

b) Write a line of code to replace (but do not actually remove, see next part of the problem) the entire inner for loop by using the prod function.

c) Add another argument to myMultProd which can either be a 1 or a 2. If it’s a 1, use the procedure in part (a). If it’s a 2, instead use the single line of code from part (b). So now your code should work like this: >> myMultProd(x,2) The output should be the same for both methods. You can check to make sure the output is correct by using the cumprod function, which does the same thing as the function you just wrote.

d) Add checks to your function that produce error or warning messages to make sure that:

- the input vector is a vector of numbers and not any other data type

- that the numbers in the vector are real (and not imaginary)

- the input vector is not a matrix - if the input vector is an empty array, then the output should also be an empty array

- the second input is a 1 or 2

Answer 1

Please find required MATLAB code along with necessary details in comments below:

--------------------------------------------------------------------------------------------------------- main_script.m

clear all; clc; close all;

x = [2 3 4 2];

myMultProd1_product=myMultProd(x,1) % actual product computed using myMultProd arg=1

myMultProd2_product=myMultProd(x,2) % actual product computed using myMultProd arg=1

actual_product=cumprod(x) % actual product computed using comprod

------------------------------------------------------------------------------------------------------------------------------ myMultProd.m

function y=myMultProd(x,arg)

if ~isvector(x) % ensure that x is a vector
if isempty(x) % check if x is empty
y=[];
end
error('Not a vector input');
return;
end

if ~isreal(x) % ensure that x has no imaginary values
error('Inputs not real');
return;
end

if ~(arg==1 || arg==2) % ensure that arg is either 1 or 2
error('Second argument invalid');
return;
end

if arg==1 % if arg is 1, use the first method
for i=1:length(x)
prodv=x(i);
for j=1:i-1
prodv=prodv*x(j); % multiply all previous values
end
y(i)=prodv;
end
elseif arg==2 % if arg is 1, use the second method
  
for i=1:length(x)
prodv=x(i);
prodv=prodv*prod(x(1:i-1)); % multiply all previous values
y(i)=prodv;
end
  
end
end

=================================== SCREENSHOT OF CODE

================================ SAMPLE OUTPUT